1. Field of the Invention
The present invention relates to a drift suppressing circuit of a gyroscope, particularly, it relates to a drift suppressing circuit of a gyroscope capable of suppressing drift components produced in the gyroscopes such as a vibrating gyroscope, an optional fiber type, a gas rate type and a rotational gyroscope which can detect a rotational angular velocity.
2. Description of the Prior Art
As a conventional vibrating gyroscope which is a background of the present invention, for example, the vibrating gyroscope, using a vibrator in which piezoelectric elements are respectively formed on three side faces of a triangular prism-shaped vibrating body, is known. In this vibrating gyroscope, for example, two piezoelectric elements are used for driving and detection and the other one piezoelectric element is used for feedback.
In such a vibrating gyroscope, when a driving signal is given from one piezoelectric element for feedback to the two driving piezoelectric elements, the vibrating body bends and vibrates. When the vibrator is rotated in such a bending and vibrating state of the vibrating body, a vibrating direction changes due to a Coriolis force and an output difference is produced between the two detecting piezoelectric elements. Thus, by measuring an output signal corresponding to the output difference, the rotational angular velocity is detected.
However, in the conventional vibrating gyroscope, due to the drift components produced by changes in environmental temperature and the like, errors are produced in the output signal, thus there is the possibility of producing errors in the detected rotational angular velocity.
Therefore, the inventor has devised a gyroscope capable of suppressing such drift components. The gyroscope comprises, an angular velocity sensor, a signal generating circuit which generates an AC signal and a composing circuit for composing the output signal of the angular velocity sensor and the AC signal generated in the signal generating circuit.
In this gyroscope, a signal corresponding to the rotational angular velocity to be detected and the drift components are output from the angular velocity sensor. Also, the AC signal is generated in the signal generating circuit. The output signal of the angular velocity sensor and the AC signal generated in the signal generating circuit are composed in the composing circuit.
When the rotational angular velocity is not applied to the angular velocity sensor, a signal corresponding to the rotational angular velocity to be detected becomes zero, and the output of the composing circuit becomes a composite signal of the drift components and the AC signal generated in the signal generating circuit. A point where an AC signal component in the composite signal becomes zero is detected, and the output of the angular velocity sensor at that point of time is regarded as the drift components.
When a correction signal corresponding to the drift components is subtracted from the output of the angular velocity sensor, the drift components are suppressed.
In this gyroscope, the drift components can be suppressed. Hence, when this gyroscope is used, even when the drift components are included in the output signal of the angular velocity sensor, the rotational angular velocity can be detected substantially without errors.
However, in this gyroscope, a circuit configuration becomes complicated because complicated circuits such as the signal generating circuit are used.
Furthermore, in this gyroscope, since the AC signal is superposed on the output signal of the angular velocity sensor to suppress the drift components, a minimum resolving power is deteriorated by an AC signal level.